spi: s3c64xx: consider the case when the CS line is not connected

When the CS line is not connected, it is not needed to enable or
disable the chip selection functionality from the s3c64xx
devices in order to perform a transfer.
Set the CS controller logically always enabled already during
initialization (by writing '0' in the S3C64XX_SPI_SLAVE_SEL
register) and never disable it.

Signed-off-by: Andi Shyti <andi.shyti@samsung.com>
Signed-off-by: Mark Brown <broonie@kernel.org>

diff --git a/Documentation/devicetree/bindings/spi/spi-samsung.txt b/Documentation/devicetree/bindings/spi/spi-samsung.txt
index 6dbdeb3c361a9973bd26a5cdcc3c73775bf8c883..930bc734927174130a3a552ff2d2a1a00d9512c4 100644 (file)
--- a/Documentation/devicetree/bindings/spi/spi-samsung.txt
+++ b/Documentation/devicetree/bindings/spi/spi-samsung.txt
@@ -40,6 +40,9 @@ Optional Board Specific Properties:
 
 - cs-gpios: should specify GPIOs used for chipselects (see spi-bus.txt)
 
+- no-cs-readback: the CS line is disconnected, therefore the device should not
+  operate based on CS signalling.
+
 SPI Controller specific data in SPI slave nodes:
 
 - The spi slave nodes should provide the following information which is required

diff --git a/drivers/spi/spi-s3c64xx.c b/drivers/spi/spi-s3c64xx.c
index 972367d5c7f219a99e579085ff1e7cdec8de3e5c..14269b07804c9565293597fbf8418e516f64333b 100644 (file)
--- a/drivers/spi/spi-s3c64xx.c
+++ b/drivers/spi/spi-s3c64xx.c
@@ -315,6 +315,9 @@ static void s3c64xx_spi_set_cs(struct spi_device *spi, bool enable)
        struct s3c64xx_spi_driver_data *sdd =
                                        spi_master_get_devdata(spi->master);
 
+       if (sdd->cntrlr_info->no_cs)
+               return;
+
        if (enable) {
                if (!(sdd->port_conf->quirks & S3C64XX_SPI_QUIRK_CS_AUTO)) {
                        writel(0, sdd->regs + S3C64XX_SPI_SLAVE_SEL);
@@ -960,7 +963,9 @@ static void s3c64xx_spi_hwinit(struct s3c64xx_spi_driver_data *sdd, int channel)
 
        sdd->cur_speed = 0;
 
-       if (!(sdd->port_conf->quirks & S3C64XX_SPI_QUIRK_CS_AUTO))
+       if (sci->no_cs)
+               writel(0, sdd->regs + S3C64XX_SPI_SLAVE_SEL);
+       else if (!(sdd->port_conf->quirks & S3C64XX_SPI_QUIRK_CS_AUTO))
                writel(S3C64XX_SPI_SLAVE_SIG_INACT, sdd->regs + S3C64XX_SPI_SLAVE_SEL);
 
        /* Disable Interrupts - we use Polling if not DMA mode */
@@ -1015,6 +1020,8 @@ static struct s3c64xx_spi_info *s3c64xx_spi_parse_dt(struct device *dev)
                sci->num_cs = temp;
        }
 
+       sci->no_cs = of_property_read_bool(dev->of_node, "broken-cs");
+
        return sci;
 }
 #else

diff --git a/include/linux/platform_data/spi-s3c64xx.h b/include/linux/platform_data/spi-s3c64xx.h
index fb5625bcca9a5b73895eac8d38d9cc3864610898..5c1e21c8727080d40ac03fe3af96b3e2f5a5e9c1 100644 (file)
--- a/include/linux/platform_data/spi-s3c64xx.h
+++ b/include/linux/platform_data/spi-s3c64xx.h
@@ -38,6 +38,7 @@ struct s3c64xx_spi_csinfo {
 struct s3c64xx_spi_info {
        int src_clk_nr;
        int num_cs;
+       bool no_cs;
        int (*cfg_gpio)(void);
        dma_filter_fn filter;
        void *dma_tx;